Add fee history rpc call (#192)

* Add fee history rpc call

* Add Changelog

Author: ferranbt

CHANGELOG.md

@@ -1,6 +1,7 @@
 
 # 0.1.2 (Unreleased)
 
+- Add `eth_feeHistory` rpc endpoint [[GH-192](https://github.com/umbracle/ethgo/issues/192)]
 - Update `testserver` to `go-ethereum:v1.10.15` [[GH-191](https://github.com/umbracle/ethgo/issues/191)]
 - Do not decode `to` in `Transaction` if not exists [[GH-190](https://github.com/umbracle/ethgo/issues/190)]
 

jsonrpc/eth.go

@@ -227,3 +227,53 @@ func (e *Eth) ChainID() (*big.Int, error) {
 	}
 	return parseBigInt(out), nil
 }
+
+// FeeHistory is the result of the eth_feeHistory endpoint
+type FeeHistory struct {
+	OldestBlock  *big.Int     `json:"oldestBlock"`
+	Reward       [][]*big.Int `json:"reward,omitempty"`
+	BaseFee      []*big.Int   `json:"baseFeePerGas,omitempty"`
+	GasUsedRatio []float64    `json:"gasUsedRatio"`
+}
+
+func (f *FeeHistory) UnmarshalJSON(data []byte) error {
+	var raw struct {
+		OldestBlock  *ArgBig     `json:"oldestBlock"`
+		Reward       [][]*ArgBig `json:"reward,omitempty"`
+		BaseFee      []*ArgBig   `json:"baseFeePerGas,omitempty"`
+		GasUsedRatio []float64   `json:"gasUsedRatio"`
+	}
+	if err := json.Unmarshal(data, &raw); err != nil {
+		return err
+	}
+	if raw.OldestBlock != nil {
+		f.OldestBlock = raw.OldestBlock.Big()
+	}
+	if raw.Reward != nil {
+		f.Reward = [][]*big.Int{}
+		for _, r := range raw.Reward {
+			elem := []*big.Int{}
+			for _, i := range r {
+				elem = append(elem, i.Big())
+			}
+			f.Reward = append(f.Reward, elem)
+		}
+	}
+	if raw.BaseFee != nil {
+		f.BaseFee = []*big.Int{}
+		for _, i := range raw.BaseFee {
+			f.BaseFee = append(f.BaseFee, i.Big())
+		}
+	}
+	f.GasUsedRatio = raw.GasUsedRatio
+	return nil
+}
+
+// FeeHistory returns base fee per gas and transaction effective priority fee
+func (e *Eth) FeeHistory(from, to ethgo.BlockNumber) (*FeeHistory, error) {
+	var out *FeeHistory
+	if err := e.c.Call("eth_feeHistory", &out, from.String(), to.String(), nil); err != nil {
+		return nil, err
+	}
+	return out, nil
+}

jsonrpc/eth_test.go

@@ -367,3 +367,17 @@ func TestEthGetStorageAt(t *testing.T) {
 		assert.True(t, strings.HasSuffix(res.String(), "a"))
 	}
 }
+
+func TestEthFeeHistory(t *testing.T) {
+	c, _ := NewClient(testutil.TestInfuraEndpoint(t))
+
+	lastBlock, err := c.Eth().BlockNumber()
+	assert.NoError(t, err)
+
+	from := ethgo.BlockNumber(lastBlock - 2)
+	to := ethgo.BlockNumber(lastBlock)
+
+	fee, err := c.Eth().FeeHistory(from, to)
+	assert.NoError(t, err)
+	assert.NotNil(t, fee)
+}

jsonrpc/subscribe.go

@@ -16,7 +16,7 @@ func (c *Client) SubscriptionEnabled() bool {
 func (c *Client) Subscribe(method string, callback func(b []byte)) (func() error, error) {
 	pub, ok := c.transport.(transport.PubSubTransport)
 	if !ok {
-		return nil, fmt.Errorf("Transport does not support the subscribe method")
+		return nil, fmt.Errorf("transport does not support the subscribe method")
 	}
 	close, err := pub.Subscribe(method, callback)
 	return close, err

jsonrpc/util.go

@@ -8,14 +8,30 @@ import (
 	"strings"
 )
 
+type ArgBig big.Int
+
+func (a *ArgBig) UnmarshalText(input []byte) error {
+	buf, err := parseHexBytes(string(input))
+	if err != nil {
+		return err
+	}
+	b := new(big.Int)
+	b.SetBytes(buf)
+	*a = ArgBig(*b)
+	return nil
+}
+
+func (a *ArgBig) Big() *big.Int {
+	b := big.Int(*a)
+	return &b
+}
+
 func encodeUintToHex(i uint64) string {
 	return fmt.Sprintf("0x%x", i)
 }
 
 func parseBigInt(str string) *big.Int {
-	if strings.HasPrefix(str, "0x") {
-		str = str[2:]
-	}
+	str = strings.TrimPrefix(str, "0x")
 	num := new(big.Int)
 	num.SetString(str, 16)
 	return num
@@ -38,7 +54,11 @@ func parseHexBytes(str string) ([]byte, error) {
 	if !strings.HasPrefix(str, "0x") {
 		return nil, fmt.Errorf("it does not have 0x prefix")
 	}
-	buf, err := hex.DecodeString(str[2:])
+	str = strings.TrimPrefix(str, "0x")
+	if len(str)%2 != 0 {
+		str = "0" + str
+	}
+	buf, err := hex.DecodeString(str)
 	if err != nil {
 		return nil, err
 	}